1. Field of the Invention
This invention relates to apparatus and methods for promoting settling of solids from waste water, and more particularly to supports for settler plates, wherein each support is provided with an integral outlet for clarified liquid flowing from an individual flow channel defined by adjacent settler plates.
2. Discussion of the Prior Art
Clarifiers (also known as "settlers") are used to remove certain materials and particles from liquid. These materials are generally suspended in the liquid and can be removed under the force of gravity when the flow of the liquid is substantially reduced, as in a very low flow, or quiescent, zone (or flow channel) in the clarifier. Since these materials are generally solid and are said to "settle" out of the liquid, they are referred to as "settleable solids". Such settleable solids may include naturally occurring materials (e.g., clay, silts, sand and dirt), chemical precipitants and biological solids. The word "solids" as used herein to describe the present invention refers to such settleable solids.
Clarifiers are used, for example, in water and waste water treatment plants. In water treatment, the water drawn from a water supply has various non-settleable colloidal solids therein. When mixed with chemicals, the colloidal solids and chemicals agglomerate to form solids. In waste water treatment, the solids include organic solids, among other wastes. Water and waste water are treated in clarifiers to remove such solids, thereby making the water clear and suitable for use, reuse, or for further treatment, such as tertiary treatment. The word "liquid" as used herein to describe the present invention refers to water and waste water.
An object of water and waste water clarifiers is to create quiescent zones having low flow rates to promote maximum settlement of solids to the bottom of the clarifiers. Clarifiers typically include a large detention basin where the settlement of the solids occurs. Tubes or flat plates mounted at fixed angles relative to the surface of the liquid have been used to form multiple thin liquid flow channels. For example, a support which may be in the form of a hollow pipe is connected to the top of one of the plates. Adjacent supports mount a pair of adjacent ones of such plates so that the adjacent plates define such a flow channel and create a quiescent zone within the detention basin in an attempt to promote settling of solids in less time using less space. The liquid containing the solids flows upwardly in the flow channels between the plates at flow rates that generally allow sufficient time for most of the solids to settle onto the plates or tubes. The hollow pipes are closed to the liquid and solids in the flow channels. Ideally, the solids then slide down the plates to the bottom of the detention basin for collection. After the solids have settled, the liquid without the settled solids is referred to as the "clarified liquid". The clarified liquid flows upwardly past the adjacent hollow pipes and out of an open top of the flow channel defined by adjacent ones of the pipes. Such open top is between and at the top of the plates. Generally, the clarified liquid from each of the separate flow channels combines to form one or more common volumes of clarified liquid above the tops of the plates and above the hollow pipes. Thus, the clarified liquid from the separate flow channels commingles and mixes in the common volume(s). The common volume(s) of clarified liquid generally flows to an outlet at an end of the retention basin and exits the basin.
As an example, in U.S. Pat. No. 5,116,443 (issued in the name of Applicant), a hollow pipe having a rectangular cross-section is shown carrying rods that support the plates. Clarified liquid from between pairs of the plates flows together (i.e., commingles and mixes as described above) and exits the end of the basin via a trough. Because the hollow pipes are closed to the liquid and solids in the flow channels, the clarified liquid does not enter the pipes. Instead, the clarified liquid flows past and above the pipes into the and then flows to the trough.
As another example, in U.S. Pat. No. 4,865,753 (issued in the name of Applicant), a flap members is provided at the top of each flow channel and releasably closes the flow channel. As the flap releases, the clarified liquid from each flow channel flows past and above the respective flap, flows together, and then exits the basin via a trough.
In yet another example, in U.S. Pat. No. 5,378,378 (issued in the name of Applicant), clarified liquid from each of many flow channels flows out of the top of a clarifier section, flows together, and then exits the basin via an outlet.
As a further example, in U.S. Pat. Nos. 4,221,671 and 5,217,614 (issued in the name of Applicant), clarified liquid from each of many tubular flow channels flows out of the top of each of the tubes, then flows together, and then exits the basin via a trough. In the '671 Patent, a perforated plate is placed over and spaced from the top of the tubes to define an overflow lauder.
As another example, in U.S. Pat. No. 5,391,306 (issued in the name of Applicant), a member is attached to the top of each of many clarifier plates to support the respective plate. Members supporting adjacent ones of the plates also control the flow of the clarified liquid from the flow channel defined by the adjacent plates. Although the members are shown as being hollow, the hollow members are closed to the liquid and solids. Therefore, the clarified liquid does not enter the members. Instead, the clarified liquid from one flow channel flows past and above the members of that flow channel, and joins clarified liquid flowing out of the other flow channels, and then the clarified liquid from all of the flow channels flows to an outlet of the basin.
An additional example is found in U.S. Pat. No. 4,136,012, wherein two clarifier outlet pipes are provided in a clarifier basin for use with over seventy tubes. Each tube defines one flow channel, such that over seventy flow channels are served by the two outlet pipes. The outlet pipes are above the tops of tubes (and thus above the tops of the clarifier flow channels) and do not support the tubes that define the flow channels. As a result, it appears that most, if not all, of the clarified liquid flowing from each tube joins together in a common volume, rises and flows into apertures formed in one or both of the two outlet pipes for flow to an outlet of the basin.
U.S. Pat. No. 4,889,624 shows a frame containing about twelve lamella plates that define separate flow channels of a clarifier. Each flow channel is defined by adjacent ones of the lammella plates. Tops of the plates are provided with legs that tend to close the upper end of each of the flow channels. To allow the clarified liquid to flow out of the flow channel, orifices are provided in the legs. The clarified liquid flowing out of one flow channel flows through the orifices of that channel, rises and and joins clarified liquid flowing out of the other flow channels. Then the clarified liquid from all of the flow channels flows over the edge of the frame to an outlet trough of the basin. It appears that a pressure drop exists across the legs, with a higher pressure being below the legs than the pressure above the legs. As a result, the higher pressure below the legs tends to lift the legs and must be counteracted by asdditional structure, such as bolts, to hold the plates down.
As a settling element in addition to adjacent plates, U.S. Pat. No. 3,963,624 shows multiple troughs adjacent to the tops of some but not all of many of the plates in a basin. As clarified liquid flows horizontally over the troughs, the troughs block any vertical flow of the liquid. With the vertical flow blocked, any entrained solids will drop out into the troughs so that the once-clarified liquid is further clarified as it flows toward a weir for exiting from the basin.
In these clarifiers, when clarified liquid exits the upper end of one particular flow channel, the clarified liquid from one flow channel generally joins with the clarified liquid from most, if not all of, the other channels. In most cases, there are at least tens of separate flow channels, such that the flow from tens of flow channels joins together and flows to an outlet trough, for example.
In the operation of many types of clarifiers, plates may become fouled when solids accumulate on the plates, for example. In such situations, it is necessary to remove the fouled clarifier plate. With the one plated removed, the two plates adjacent to the fouled plate cooperate to define a now-wider one of the flow channels. Problems result when a prior art plate of the type shown in U.S. Pat. No. 4,889,624 is removed. For example, without the removed plate and the legs at the top end of the removed plate, there is no leg to restrict the flow of the clarified liquid out of the top of the original flow channel. As a result, it is likely that there will be an increased flow rate of liquid and solids in the now-wider channel between the two remaining adjacent plates, less settling in that now-wider channel, less clarified liquid for a given inflow of solids, and thus more solids flowing out of the now-wider channel. The increased flow rate tends to disturb the flow rates in the other channels, such that the operation of the clarifier may have to be interrupted during repair of the plate.
In other types of clarifiers without such legs at the top of the flow channels, there would be the same flow rate of liquid and solids in the now-wider channel between the two remaining adjacent plates. However, because of the removal of the middle plate, the vertical settling distance between the two remaining settler plates is now twice the former vertical settling distance. Therefore, because the flow of the liquid in the now-wider flow channel is the same as before removal of the middle plate, less of the solids will move vertically downward onto the lower of the two remaining plates, and therefore less of the solids will settle. To avoid allowing the less clarified liquid from the now-wider flow channel to flow to the trough, the operation of the clarifier may have to be interrupted during repair of the removed plate.
Also, in many clarifiers, the support for a particular plate tends to block the upward flow of the clarified liquid. Such blockage results, for example, from the need to increase the size of the support to increase the strength of the support and prevent sagging of the support as it extends across the clarifier basin. Even when the sagging problem is overcome with a minimum of such blockage, the prior supports, the clarified liquid from different flow channels still combines in the space above the flow channels.
Therefore, what is needed is a separate support for each settler plate, wherein each separate support reduces the blockage of clarified liquid from a flow channel and not only carries the one settler plate, but is also provided with an integral inlet for receiving clarified liquid flowing from flow channels adjacent to the separate support, and preferrably, for receiving clarified liquid primarily from one individual flow channel defined in-part by the settler plate carried by the one separate support.